mapping removal swelling clay soils in the...

AAnnaalleellee UUnniivveerrssiittăăţţiiii ddiinn OOrraaddeeaa,, SSeerriiaa GGeeooggrraaffiiee Year XXXXVVII, no. 22//22001166 (December), pp. 114433--115522ISSN 11222211--11227733, E-ISSN 22006655--33440099 Article no. 226622110033--669955

http://istgeorelint.uoradea.ro/Reviste/Anale/anale.htm

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RRaahhmmaannii MMOOUUNNAA Science Department of Earth, Faculty of Science, University of Batna, Algeria

e-mail: [email protected]

BBaahheeddddii MMOOHHAAMMEEDD Department of Civil Engineering, Faculty of Engineering, Batna University, LRNAT Laboratory, Algeria


Mahdi KALLA Department of Civil Engineering, Faculty of Engineering, Batna University, LRNAT Laboratory, Algeria


Abstract: The shrinkage and swelling phenomena of certain clay soils cause differential settlement manifested by disorders that affect mainly the individual frame. The objective of this research was to create a map related to these phenomena especially in the area of Algeria N’gaous (figure 1). The approach of the study is primarily based firstly on the interpretation of a geological map at a scale 1 : 50 000 and on the other part from existing literature and observations on a synthesis of a large number of geotechnical information to determine susceptibility to the phenomenon of clay or marl formations. This approach consisted in the establishment of a synthetic departmental mapping of these formations that have been identified from a hierarchy as to their susceptibility according to the shrinkage and swelling phenomenon. This classification was established on the basis of three quantifiable main features: the dominant lithology of formations, the mineralogical composition of their clay fraction (proportion of swelling minerals) and geotechnical behavior (primarily assessed from the blue value and the plasticity index). Key words: marl, smectite, shrinkage and swelling, natural risk, geotechnical mapping,

* * * * * *

INTRODUCTION The phenomena of shrinkage and swelling clays are the source of many disorders in the

frame and constitute the world's second leading cause of natural disasters compensation after floods. Indeed, alternating periods of drought and precipitation leads to changes in the soil water status resulting in displacement of shallow foundations induced by hydro-mechanical couplings.

Corresponding Author

Rahmani MOUNA, Baheddi MOHAMED, Mahdi KALLA

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This alternation of withdrawals and swelling can cause damage in the built form of relatively large cracks or the partial or total disruption of that work, when not included in the projects.

The swelling clays are present in several regions of Algeria. The damage to infrastructure in this type of land totaling several billion dinars annually. These excessive damages are due in part to inappropriate design, resulting from the lack of tools to assess the impact of expansive soils in typical applications. This research work presents an experimental program and interpretations in order to establish an objective scientific fact and to have references to preventive information, to map this phenomenon in the region N'GAOUS to define the most exposed areas in shrinkage and swelling clays (AFNOR, 1998; Mamoune, 2002; Bekkouche, 2005; Derriche & Kaoua,1994; Djedid et al., 1997; Philipponnat, 1991).

Figure 1. Presentation card of study area N’gaous Algeria Region

IDENTIFICATION AND MAPPING OF CLAY AND MARL N'GAOUS

GEOLOGICAL FORMATIONS IN THE AREA The goal is to have a map of geological formations and clay marl of N'gaous area to

identify areas susceptible to shrinkage and swelling. This work was carried out from the 1:50 000 geological maps covering the entire area from

which we selected the clay and marl formations that may be prone to shrinkage and swelling phenomenon. It was identified 32 levels with this character on the area (table 1).

In some cases, the clay or marl constitute the major part of the retaining formation. But in most cases, the clay or marl geological formations N'gaous area is very heterogeneous; it could be criteria. The criteria for the development of the susceptibility map withdrawal - swelling

Mapping Removal Swelling Clay Soils in the Aures (N´gaous) Algeria

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phenomenon are the lithology of the formations, the characterization of these formations depending on the mineralogical nature of these clays in the clay phase and the geotechnical behavior of the material. The susceptibility map and either intrinsically heterogeneous formations, which consist of a mixture of different materials including clays or marls, but also coarser elements (silts, sands, serious ...). This is particularly the case of alluvial formations, variegated sands and clays, clay, sand and sandstone Ypresian, black sands and clays. The clay is either mixed with the other constituents, either in the form of individualized levels, separated from each other by spacers of non-clay beds, distributed in a complex sequence and which may exhibit spatial variations. In these circumstances it is not possible, at the departmental level, to accurately distinguish the clay-containing those areas where it is completely absent, and all of these courses, for heterogeneous nature was considered like clay; or formations to the little clay base, but which, because of their alteration, present in many sectors clay facies, especially in the first few meters of soil. Again, due to the impossibility of distinguishing at the departmental level the contours of clay areas of those indurated zones (notably limestone), it was decided to consider all of these formations like clay, especially because of many claims they have caused.

The heterogeneity of this training course is taken into account in the characterization of susceptibility with respect to the shrinkage and swelling, particularly in the lithological rating (figure 2).

Table 1. List of clay and marl formations of the Region N'gaous N° Code Geological formation name 1 m3b gypsum marl and sandstone 2 c2b Calcareous-marl alternations 3 c2a limestone and flint rudist 4 c1d Saccharoides dolomites, massive Claires 5 c5-6a marls with small limestone beds 6 c3-4 marls with small limestone beds 7 m1 red pudding and marnolites 8 m4 Sanders brown marl, sandstone, gypsum 9 p1-2 sandstone and sandy loams 10 q4 coarse conglomerate 11 m2-3 conglomerates, breccias, limestones has lithothamniées 12 t3 compact limestone and crusts 13 t6 soft carbonate deposits 14 t4 porous limestone and crusts 15 q5 sandy clay to calcareous dolls 16 q undifferentiated quaternary 17 q6 silts, conglomerates 18 t5 porous limestone powder, white 19 t7 very soft clay deposits -carbonatés 20 q6-7 silt, pebbles and sand, conglomerates 21 q2 very coarse conglomerate 22 q3 very coarse conglomerate 23 m3a limestones lithomanieés 25 c2b Calcareous-marl alternations 26 m2a calcareous conglomerates lithothamniées 27 éboulis scree 28 terrasse teracce 29 q5-6 sandy clay to calcareous dolls, silts 30 q1 conglomerate block 31 q7 silt, pebbles and sand 32 m2b sandy marl and calcareous marl


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Figure 2. Geological Map of the Region N'gaous

CHARACTERIZATION LITHOLOGICAL, MINERALOGICAL AND

GEOTECHNICAL CLAY FORMATIONS - DEVELOPING THE SUSCEPTIBILITY MAP Criteria The criteria for the development of the susceptibility map withdrawal-swelling

phenomenon are the lithology of the formations, the characterization of these formations depending on the mineralogical nature of these clays in the clay phase and the geotechnical behavior of the material. The susceptibility map and developed corresponds to a prioritization of identified geological formations, taking into account only these three criteria.

Classification procedure We remember that the basic document used to develop the susceptibility map is the

synthetic clay and marl map courses of the department, which was established with primary nature of the lithological formations.

The second step of this mapping is to prioritize training marly clay and thus identified, based on their greater or lesser susceptibility according to the shrinkage and swelling phenomenon.


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This ranking is based on the consideration of quantifiable characteristics, estimated for each of the 31 selected courses:

- the lithology of the land constituting the majority of training; - the mineralogical composition of the clay fraction, assessed from the proportion of

swelling minerals; - the geotechnical behavior of the material, evaluated primarily from the reactivity of the

soil respecting water (characterized by the value of blue, the extent of its plastic domain (characterized by its plasticity index).

In order to obtain a practical way to prioritization between the different formations, the rule adopted was to use threshold values commonly accepted in the literature, distinguishing four levels of sensitivity (low, medium, high and very high). To enable the realization of calculations, large distinguished lithological classes were also affected by a note. For the three natural features of the land, this allows to assign a score from 1 to 4 in each of marl or clay formations identified in (table 2).

Criteria lithology

Table 2. The scale used to distinguish the different lithological classes is:

Formation type

Susceptibility

Lithologic Note

Non-clay formation but locally containing past or clay pockets (eg alluvium with clay lenses, limestone pockets karst, ...) low 1

Training with a term not predominant clay or sandy clay calcareous clayey average 2

Training predominantly clay, with a term or not passed clay (eg alternating marl limestone or sandy clay) or very thin (within 3 m) forte 3

Mainly clay marl or training, over 3 m in thickness and continuous very strong 4

The classification following lithological rating highlights the fact that among the 32 clay or

marl geological department (table 3): - 3 training get a rating of 3, which means that their clay component is dominant; - 8 formations obtain a score of 2, which means that the term clay is not predominant; - 15 trainings get a rating of 1, indicating that the clay are terms that are present very locally; - no training has been rated 4.

Table 3. The scores for each lithological formations are presented below

N° Code Name of the geological formation lithological Note 1 m3b gypsum marl and sandstone 2 2 c2b Calcareous-marl alternations 3 3 c2a limestone and flint rudist 1 4 c1d Saccharoides dolomites, massive Claires 0 5 c5-6a marls with small limestone beds 2 6 c3-4 marls with small limestone beds 2 7 m1 red pudding and marnolites 0 8 m4 Sanders brown marl, sandstone, gypsum 2 9 p1-2 sandstone and sandy loams 2

10 q4 coarse conglomerate 1 11 m2-3 conglomerates, breccias, limestones has lithothamniées 1


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12 t3 compact limestone and crusts 0 13 t6 soft carbonate deposits 1 14 t4 porous limestone and crusts 1 15 q5 a calcareous sandy clay dolls 2 16 q undifferentiated quaternary 1 17 q6 silts, conglomerates 1 18 t5 porous limestone powder, white 1 19 t7 very soft clay deposits -carbonatés 3 20 q6-7 silt, pebbles and sand, conglomerates 1 21 q2 very coarse conglomerate 1 22 q3 very coarse conglomerate 1 23 m3a limestones lithomanieés 0 25 c2b Calcareous-marl alternations 3 26 m2a calcareous conglomerates lithothamniées 0 27 scree scree 1 28 terrace terrace 1 29 q5-6 a calcareous sandy clay dolls, silts 2 30 q1 conglomerate blocks 1 31 q7 limon, galets et sables 1 32 m2b marnes et marno-calcaires sableux 2

CARACTERISATION MINERALOGIQUE CLAY FORMATIONS Chemical analysis: This analysis included the determination of the chemical nature of the

clay N’Gaous to study. In this context, a quantitative chemical analysis by XRF was determined; the results are summarized in the table below:

Table 4. Chemical composition of N’Gaous clay

Chemical composition Quantities (%) Silica [SiO2] alumina [Al2O3] Iron oxide [Fe2O3] Calcium carbonate [CaCO3] Lime [CaO] Magnesia [MgO] sulfur trioxide [SO3] K2O Na2O

41,78 17,43 7,43 7,92 7,32 2,72 0,02 2,03 0,37 0,02

Thus, the quantitative chemical analysis reveals that: - the sample contains an amount of 41.78% silica [SiO2] well below 80% which is the

border of expansive soils and non-swelling; - the rate of calcium carbonate [CaCO3] is 7.92% so that the clay to be tested is actually clay; - the rate of sulfuric anhydride [SO3] is 0.02% so that the clay to be studied is not

aggressive reality. MAP SUSCEPTIBILITY Map of the susceptibility region was drawn from the synthetic clay and marl map of

formations, assigning to each of geological susceptibility class defined above. The white areas of the map correspond to the non-argillaceous formations a priori, and therefore theoretically not subject to shrinkage and swelling phenomenon. However, one cannot exclude that these formations are covered locally superficial veneer of clay or contain pockets of clay, not drawn to


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scale geological map of the current. These elements are linked in particular to formations of heterogeneity of mainly sand may locally contain clay lenses or alteration of carbonate formations.

Clay and marl formations are represented by two colors (yellow or orange) according to their respective degree of susceptibility increasing the phenomenon of low and moderate shrinkage and swelling (figure 3).

Figure 3. Geological map of training component has Clayey or Marl in the Region of N'gaous


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Figure 4. Map susceptibility to shrinkage and swelling clays in Region of N'gaous

Table 5. Training susceptibility Degree

N° Code Name of the geological formation Note

lithological

Note mineralogical

Note géotechniq

ue

Moyenne

Degree of susceptibility

1 m3b gypsum marl and sandstone 2 2 3 2,33 average 2 c2b Calcareous-marl alternations 3 2 3 2,67 average 3 c2a Limestone and flint rudist 1 2 3 2,00 weak

4 c1d Saccharoides dolomites, massive Claires 0 0 0 -


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5 c5-6a marls with small limestone beds 2 2 3 2,33 average 6 c3-4 marls with small limestone beds 2 2 3 2,33 average 7 m1 red pudding and marnolites 0 0 0 -

8 m4 Sanders brown marl, sandstone, gypsum 2 2 3 2,33 average

9 p1-2 sandstone and sandy loams 2 2 3 2,33 average 10 q4 coarse conglomerate 1 2 3 2,00 weak

11 m2-3 conglomerates, breccias, limestones lithothamniées 1 2 3 2,00 weak

12 t3 compact limestone and crusts 0 2 3 1,67 weak 13 t6 soft carbonate deposits 1 2 3 2,00 weak 14 t4 porous limestone and crusts 1 2 3 2,00 weak 15 q5 sandy clay to calcareous dolls 2 2 3 2,33 average 16 q undifferentiated quaternary 1 2 3 2,00 weak 17 q6 silts, conglomerates 1 2 3 2,00 weak 18 t5 porous limestone powder, white 1 2 3 2,00 weak 19 t7 very soft clay deposits -carbonatés 3 2 3 2,67 average

20 q6-7 silt, pebbles and sand, conglomerates 1 2 3 2,00 weak

21 q2 very coarse conglomerate 1 2 3 2,00 weak 22 q3 very coarse conglomerate 1 2 3 2,00 weak 23 m3a limestones lithomaniées 0 2 3 1 ,67 weak 24 c2b Calcareous-marl alternations 3 2 3 2,67 average

25 m2a calcareous conglomerates lithothamniées 0 0 0 -

26 scree scree 1 2 3 2,00 weak 27 terrace terrace 1 2 3 2,00 weak 28 q5-6 sandy clay to calcareous dolls, silts 2 2 3 2,33 average 29 q1 conglomerate blocks 1 2 3 2,00 weak 30 q7 silt, pebbles and sand 1 2 3 2,00 weak 31 m2b sandy marl and calcareous marl 2 2 3 2,33 average

CONCLUSION The objective of this study was to establish maps on the phenomenon of shrinkage and

swelling of clay soils in the N’Gaous region (Algeria). The approach is essentially based on an interpretation of the geological map and the synthesis of a large amount of information regarding susceptibility to the phenomenon of predominantly clay formations.

Synthetic map identifies the final 32 clay and marl formations, one of whose characteristics is the high heterogeneity related to their training condition or weathering.

The training was identified and prioritized according to their susceptibility to shrinkage and swelling phenomenon.

This classification was established on the basis of three main quantifiable characteristics (nature lithological, mineralogical composition and geotechnical behavior of soils). In addition, some factors of purely local expansion, such as tree vegetation, some human actions defects or foundation, were not taken into account as part of a study conducted. Others, such as the hydrogeological context, the geographical distribution of water deficits and topographic configuration were not considered sufficiently discriminating to be considered in the development of the mapping of the area

Ultimately, this card could serve as a basis for preventive actions information in the most affected by the phenomenon Commons. It would also be a prerequisite for the development of the Natural Hazards Prevention Plans (PPR), to attract the attention of builders and building owners on the need to respect certain preventive building codes in areas. This regulatory tool should


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emphasize the importance of a geotechnical study as a prerequisite for any new construction in areas affected by the geological formations with high, medium and low susceptibility, particularly because of their strong heterogeneity. Otherwise, it should implement constructive rules to reduce the risk of occurrence of claims.

REFERENCES AFNOR (1998), Geotechnical: soil identification tests, Volume 1, Edition Afnor, 2nd Edition, Paris, France. Behavior of expansive soils, Magister Submission to Departmentof civil engineering, University A. Belkaïd, Tlemcen,

Algeria. Bekkouche (2005), Soil stabilization techniques expansive study days of Expansive soils, A. Belkaïd University, Tlemcen,

Algeria. Derriche Z., Kaoua F. (1994), Swelling soils: the works of design methodology for ENTP Review Technique; Algeria

Equipment. Djedid A., Bekkouche A., Bousmaha N. (1997), Building on expansive soils, National Engineering Symposium, University

Center Mohamed Boudiaf, Msila. Mamoune Aissa (2002), Contribution to the measurement, prediction and modeling. Philipponnat G. (1991), Removing swelling clays, proposed methodology. French Geotechnical Journal.

Submitted: Revised: Accepted and published online Octomber 25, 2015 June 20, 2016 September 19, 2016

mapping removal swelling clay soils in the...

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